Synchronized analyte testing system

ABSTRACT

An analyte detection system is provided with calibration information uniquely specific to the set of test strips to which the sample is to be applied. The calibration information may be stored in permanent memory of the testing device, such that the device is discarded after use of all the test strips in a kit, or it may be stored in a calibration chip accompanying the set of test strips and distributed therewith, thereby enabling re-use of the testing device with a different set of test strips and associated calibration chip.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to detection devices fordetermining the presence or concentration of analytes or biologicalagents in a sample, and more particularly, to systems using testinginstruments to measure analyte activity on test strips impregnated withappropriate reagents.

[0003] 2. Description of Related Art

[0004] The need for simple methods to determine the chemical andbiological constituents in bodily fluids has increased as point of caretesting has gained in popularity. A common application is the selfmonitoring of blood glucose concentrations by patients with diabetes.These patients frequently administer insulin or take other therapeuticactions based on the test results. As testing is generally recommendedmultiple times daily and may occur in any setting, an easy to use andrelatively inexpensive method to accomplish this task is required. Thecosts of testing are significant to many diabetic patients, especiallyelderly patients with fixed incomes and those who are not reimbursed byhealth insurance plans.

[0005] In addition to chronic disease monitoring, there are otherapplications where simple, low cost testing at the point of care may bedesired. For example, many practitioners believe that certainmedications could be administered much more effectively, both from amedical outcomes and from a cost perspective, if the circulating levelof such medications could be monitored during the course of treatment.Generally, if the level of an analyte or biological agent is importantenough, the patient needs to go to a clinic or laboratory and submit toa venipuncture so a test may be run on an expensive clinical instrument.The ability to inexpensively monitor the patient either in the doctor'soffice or at home could lead to improved outcomes. Given the currentpressures on improving the cost effectiveness of health care,inexpensive, easy to use alternatives to expensive test methods would bewelcomed.

[0006] The National Institutes of Health conducted a large scale studyto evaluate the benefit of long term tight control of the blood glucosefor the diabetic patient. The study, known as the DCCT, proved that longterm tight control of the blood glucose levels in patients had a directrelationship to the health of the patient. One way for the medicalprofession to monitor the control of a patient is for the patient to usea blood glucose monitoring system which has a memory unit to record theblood glucose level and other data such as date and time.

[0007] Many diabetics currently use a test method described in U.S. Pat.No. 5,304,468 to Phillips et al. This system is comprised of anelectronic meter and a disposable reagent strip. The meter reads thecolor change of the strip which correlates to the concentration of theanalyte in the sample applied to the strip. The meter is an expensiveand complex instrument which uses multiple light sources or detectors toisolate the reagent color change from the sample color. The user mustselect the calibration code for the meter to match the calibration codeof the test strips. In this way, the meter accommodates a wide range oftest strip performance values.

[0008] U.S. Pat. No. 4,637,403 to Garcia et al. describes an integratedsystem which provides a method by which the patient lances the finger toget a sample of blood which is then used by the device to read thequantity of analyte in the sample. This system uses a complexreflectance system to read the analyte level in the sample.

[0009] U.S. Pat. No. 5,279,294 to Anderson et al. describes a hand heldshirt pocket device for quantitative measurement of glucose or analytesin biological fluids. The device has a sophisticated electronics systemand a sampling system integrated into one device to determine thequantity of analyte in a bodily fluid sample

[0010] U.S. No. Patent 5,515,170 to Matzinger et al. describes thedifficulties of keeping a strip holder and optics system clean and theneed to present the test strip in the proper perspective to the optics.

[0011] European Patent Specification 0 351 891 B1 Hill et al. describesan electrochemical system and electrodes which are suitable for the invitro determination of blood glucose levels. The system requires the useof expensive electrodes and a sophisticated reader to determine bloodglucose levels.

[0012] U.S. Pat. No. 4,994,167 to Shults et al. describes a measuringdevice for determining the presence and amount of a substance in abiological fluid using electrochemical methods. This system requires acomplex instrument and method for the patient to determine thequantitative result.

[0013] U.S. Pat. No. 5,580,794 to Allen et al. describes a single usedisposable measuring device for determining the presence and amount of asubstance in a biological fluid using reflectance methods. This systemutilizes an optics and electronics package which are mated in a singleplane.

[0014] Single use disposable devices have been designed for the analysisof analytes in bodily fluids. U.S. Pat. No. 3,298,789 to Mast describesa system in which whole blood is applied to a reagent strip. After aprecise, user-timed interval, the blood must be wiped off by the user.An enzyme system reacts with the glucose present in the sample to createa color change which is proportional to the amount of glucose in thesample. The strip may be read visually, by comparing to a printed colorintensity scale, or in an electronic instrument.

[0015] U.S. Pat. No. 5,418,142 to Kiser et al. describes a single usedevice which does not require blood removal or color matching. Theamount of analyte present in the sample is read in a semiquantitativefashion.

[0016] U.S. Pat. No. 5,451,350 to Macho et al. describes a single usesystem for the determination of an analyte in a biological sample.

[0017] U.S. Pat. No. 5,522,255 to Neel et al. describes a fluid dose,flow and coagulation sensor for a medical instrument which uses anon-volatile electronic calibration device in the system to check thecalibration of the reagent strip.

[0018] U.S. Pat. No. 5,053,199 to Keiser et. al. describes anelectronically readable information carrier for use with a medicaldevice.

[0019] U.S. Pat. No. 5,366,609 to White et. al. describes a biosensingmeter with a pluggable memory key. This device uses a pluggable memorykey which is used to control the operations of the meter.

[0020] U.S. Pat. No. 5,307,263 to Brown describes a modularmicroprocessor based health monitoring system designed to collect datafrom a health monitoring test system such as a blood glucose monitoringmeter.

[0021] Although many improvements have been made, the cost andcomplexity of measuring analyte levels in biological samples remains asignificant issue for patients and for the health care system. Evenpatients who are covered for blood glucose monitoring supplies mustoften purchase the meter and await reimbursement. The need to match thecalibration of a meter and the strips or electrodes in use leads toerrors in performance and adds cost and complexity for themanufacturers. The availability of a low cost, simplified quantitativetest system for the periodic monitoring of constituents of biologicalfluids, such as glucose in blood, would make testing more accessible topatients and would improve their well-being and reduce the cost of theircare.

[0022] Currently, existing calibration mechanisms require the loading ofa calibration chip, calibration strip, inputting of a calibration codeor use of a machine readable mechanism on the strip to modify thereaction interpretation of the meters. These methods can result inerrors in reading of the analyte being tested for by using either thewrong calibration device with a lot of strips or entering the wrongcalibration code for the lot of strips.

[0023] In addition, a system which requires a smaller fluid sample wouldbe attractive to many patients. There has been a trend toward smallersample sizes, but most devices still require about 10 μL of blood. Manypatients have difficulty routinely applying an adequate sample to thestrips or electrodes. Inadequate sampling can cause erroneous results ormay require that the user discard an expensive test strip and repeat thesample application procedure.

[0024] An additional issue is the use of out of date test strips withthe meter. Currently the expiration date and expiration period afteropening is printed on the container for the test strips. This presents aproblem for the patient if he or she does not observe the datinginformation on the container. The strips can result in an error in thereading which can cause false response/treatment by the patient.

SUMMARY OF THE INVENTION

[0025] The invention overcomes the deficiencies of the prior art byproviding a low cost testing instrument and single use test stripscapable of reading small sample sizes, e.g. 3 μL, and determining theamount of an analyte in the small sample. The low cost nature of thetesting instrument permits the packaging of the testing instrument andtest strips together in a package, creating a synchronized system whichmay be used to perform a specific number of tests. The testinginstrument is provided at no extra cost to the user, who benefits fromhaving a fresh device with each new package of test strips purchased.This eliminates the need for the patient to make an investment in testequipment to monitor a specific condition or therapy.

[0026] In an alternate configuration, the device may be provided as partof a starter package including a sampling device and test strips.Replacement test strips could be purchased separately without the deviceor sampler if longer testing instrument life is preferable. For example,the desire to include additional features such as data managementcapabilities could add cost which would favor a longer useful life forthe-testing instrument.

[0027] The testing instrument incorporates a molded lens optic systemconsisting of one or more channels and a simple electronics packageconsisting of light emitting diodes (LEDs), analog to digital conversionelectronics, a processor unit, Read Only Memory and a digital displaysystem. The testing instrument case has a positioning system whichinterfaces with the test strip to create positive location and alignmentfor the reagent test pad within the strip and the optics.

[0028] The applied bodily fluid reacts with the reagents impregnated inthe test pad within the test strip and the resulting color change isread by the optics system. The signal is converted and displayed on thedigital readout as the concentration of the analyte in the sample.

[0029] An advantageous feature in accordance with the invention is theuse of a small sample sizes, e.g., about 3 μL, which is a fraction ofthe volume required for most blood glucose tests and could be morereadily obtained by patients.

[0030] Another advantageous feature in accordance with the invention isthe provision of a simple low cost testing instrument and acomplimentary reagent test strip.

[0031] Another advantageous feature in accordance to the invention isthe use of reagent test strips that are calibrated to the testinginstrument and/or an intelligent calibration device which may each beone-time readable mechanisms, eliminating the potential problems ofre-use of the calibration device with the wrong set of test strips.

[0032] Another advantageous feature in accordance with the invention isa testing instrument which is precalibrated or synchronized to the lotof reagents test strips with which it is supplied, eliminating the needfor the user to match or enter calibration information.

[0033] Another advantageous feature in accordance with the invention isa system which is designed for a predetermined number of test results,minimizing upkeep such as cleaning or battery replacement.

[0034] Another advantageous feature in accordance with the invention isthe elimination of the need for a separate test strip holder,simplifying the interface of the disposable portion of the test systemwith the re-usable testing instrument.

[0035] Another advantageous feature in accordance with the invention isthe elimination of the need for a patient to calibrate the meter for thetest strips or keep track of expiration dating by placing theinformation on a single use calibration chip.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Many advantages of the present invention will be apparent tothose skilled in the art with a reading of this specification inconjunction with the attached drawings, wherein like reference numeralsare applied to like elements and wherein:

[0037]FIG. 1 is a perspective view of one embodiment of a test stripcomprised of a test pad and holder for body fluid analysis.

[0038]FIG. 2 is a perspective view of one embodiment of the testinginstrument having a test pad holder.

[0039]FIG. 3 illustrates the testing instrument and a test strip incommunication with the test strip.

[0040]FIG. 4 is a block diagram of the testing instrument electronicsand optics for reading the test strip.

[0041]FIGS. 5A and 5B illustrate a method of confirming the wetting ofthe test pad and contact to start the timing of the testing instrument.

[0042]FIG. 6 shows a kit of the system including testing instrument andtest strips.

[0043]FIG. 7 shows a kit of the system including testing instrument,test strips and sampling devices.

[0044]FIG. 8 shows the use of two detectors and two emitters in anoptics system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045]FIG. 1 is a perspective view showing the test strip 11 for usewith the detection device in accordance with the invention, the teststrip 11 comprising a test pad 12 and holder 13 for analysis of bodilyfluid 16. The test strip 11 provides a handle 14 for the patient to holdthe strip 11. The handle operates as a wick to transfer the bodily fluid16 to the test pad 12 and is provided with a channel 10 for thispurpose. The test pad 12 may be formed from bibulous matrix which hasbeen impregnated with a reagent system comprised of enzymes, indicatorsand blood separation agents.

[0046] Test strip 11 is provided with an alignment mechanism which maycomprise recess 17 and projection 18 disposed on bottom portion 15 ofthe test strip 11. These operate to insure positive location andorientation of the test strip 11 with respect to the testing instrument21 of the invention by engaging corresponding portions of the testinginstrument as explained below. Of course it is contemplated that othertest strip configurations can be used with the system of the inventionwithout patentable departure from the spirit and scope of the invention.

[0047]FIG. 2 is a perspective view of testing instrument 21 which isused to read test strip 11 in accordance with the invention. The testinginstrument 21 has a housing 22 which is provided with optics view window23 and a docking portion 37 for mating with alignment recess 17 andprojection 18 of test strip 11. Docking portion 37 may comprise a slot20 disposed in a retaining clip 19 which operates to guide handle 14 oftest strip 11 into position, along with a recess 24 to mate withprojection 18 of the test strip 11. Proper alignment for accuratereading is thereby insured, as illustrated in FIG. 3, which shows thetesting instrument 21 in operational position in communication with thetest strip 11.

[0048] Testing instrument 21 is also provided with a sensor 45 formeasuring the analyte concentration in sample 16, along with a display49 for displaying the result. The sensor 45 may be optical in nature,and as shown in FIG. 8, may comprise paired light emitter and detectordevices. Specifically, an LED emitter 50 and A photodetector 51 measurereflected light from the sample-containing test pad 12. This reflectedlight is proportional to the amount of analyte in the sample asmanifested by the extent of reaction of the sample/analyte with thereagent on the test pad 12. Ambient light is blocked by a design of teststrip 11 and testing instrument 21 which minimizes error induced byambient light corrupting the reflectance reading. Such a design mayinclude appropriately limiting the size of view window 23 whileselecting sufficiently opaque materials to form the material of thehousing 22 from, which view window 23 is formed, thus operating toeffectively form an optical shield. Insuring proper alignment inaccordance with the invention also serves to minimize ambient lightcorruption.

[0049] In accordance with the invention, numerous optical schemes may beemployed, including use of transmitted rather than reflected light,multiple LED/detector pairs and various arrangements thereof. It is alsocontemplated that various light source:light detector ratios maybe used,departing from the one-to-one correspondence disclosed.

[0050] In accordance with the invention, an LED 53 is also provided andcorresponds with a photodetector 52. The photodetectors 51 and 52 may beselected to operate at different light intensity levels, such that lightbelow or at a predetermined intensity threshold is measured by onephotodetector, while light above the threshold is measured by the otherphotodetector. Alternatively, one detector can be used to measurereflectance of a particular color component, while the other measuresthe reflectance of a different color component, or one detector canmeasure overall light intensity while the other measures a colorcomponent. Also, a reference detector (not shown) could be employed tocompensate for the deterioration of the LED intensity over time. Inalternative arrangement, the measurement from one detector can be usedto provide a compensation for hematocrit level or oxygen content of theblood. One of ordinary skill in the art will realize many modificationsand remain within the purview of the invention.

[0051] An optical arrangement in accordance with the invention isfurther provided with a molded plastic lens system 48 to focus light toand from the sample on the test pad 12. Such an arrangement provides thecapability of focusing the light to and from a small reaction area,which reduces the size of the test pad 12 and the amount of samplerequired to effect the testing procedure. Advantages thus realizedinclude reduction in size/cost of the matrix employed and quantity ofexpensive reagents required.

[0052] The optics of the invention may include appropriate opticalfiltering to optimize measurement, or electronic filtering and maskingtechniques may be employed to improve signal-to-noise levels. An opticalfiltering scheme of the invention, when blood analysis is to beperformed, involves the use of existing membrane materials with ablocking filler to create an opaque membrane which blocks interferencefrom red blood cells and can assist in the separation of red blood cellsfrom relatively clear fluid.

[0053] Another optical configuration uses multiple LED and photodetectorpairs. A first pair is used to achieve the primary analytedetermination. A second pair is used to monitor test initiation and toquantify hemoglobin and hematocrit. Subsequent pairs are used to monitornative color effects of lympic and icteric samples. Additional opticalpairs are used in association with added chemical components in thestrip for specific determination of possible interference factors suchas pH, specific gravity, etc. as well as for specific determination ofadditional analytes such as cholesterol, triglycerides, etc. Suchanalysis, possibly using different wavelengths, provides significantbenefits to overcoming interfering effects from the sample and theenvironment. By selecting wavelength pairs which are tuned to detectcomponents of the test, it is possible to isolate and quantify theanalyte, hematocrit and red blood cell contributions in a testing event.In accordance with the invention, interference from the environment isminimized by separating its effects and monitoring each oneindependently using multiple optical systems. Through detection andquantification, the individual contribution to the measurement can besubtracted from the analyte measurement. With the ever decreasing costof computing power, and a unique of constructing multiple opticalsystems at very low cost, the approach of the invention is readilyapplicable to home diagnostic use.

[0054] The test strip 11 is comprised of a test pad 12 situated in atest pad holder 13. This holder provides a means for accuratelypositioning the test pad 12 with respect to the sensor 45 in addition toproviding a means for blocking ambient light from effecting theanalysis. The test pad 12 is impregnated with the appropriate chemistryto permit a colormetric analysis of the analyte being tested and maytherefore provide a stable absorbent substrate.

[0055] The test strip 11 of this invention differs from current teststrips in multiple ways. For current test strips, the nonporous supportprovides a handle for the patient [U.S. Pat. No. 5,526,120 Jina et al.],and/or a means of aligning the test strip in a strip holder [U.S. Pat.No. 5,515,170 Matzinger et al.] The test strip of this invention doesprovide a support for the test pad. The strip positively seats on thetesting instrument, assuring proper alignment. It also seals the opticsarea from ambient light and blood contamination. Thus it provides all ofthe functionality of a test strip and test strip holder of aconventional reflectance system. The test strip provides additionalbenefits in being removed after each test, facilitating easy access tothe optics area for cleaning if required. With this combination part,the overall cost of the system is further reduced. When inserted intothe detection device 21, the test strip 11 contacts complete a circuitwhich turns the device on. The device is turned off upon removal of thetest strip. This eliminates a need for a separate on/off circuit orpatient action to turn the testing instrument on or off.

[0056] The signal producing system impregnated in the test pad matrixcan be formed from different indicator systems such as3-methyl-2-benzothiazolinone hydrazone (MBTH) and8-anilino-1-naphthalenessulfonate(ANS) [U.S. Pat. No. 5,453,360 Yu],MBTH and 3-dimethylaminobenzoic acid (DMAB) [U.S. Pat. No. 5,049,487Phillips et al.], 3-methyl-2-benzothiazolinone-hydrazone-sulfonatesodium salt (MBTH-SO₄) and ANS [U.S. patent application Ser. No.08/628,794 Douglas et al.], MBTH-SO₄ and N-(3-sulfopropyl)aniline(HALPS) [U.S. Pat. No. 4,396,714 Maeda et al. and U.S. patentapplication Ser. No. 08/628,794 Douglas et al.], MBTH-SO₄ andN-Ethyl-N-(3-sulfopropyl)aniline ALPS [U.S. Pat. No. 4,396,714 Maeda et.al. and U.S. patent application Ser. No. 08/628,794 Douglas et al.]. Oneskilled in the art could devise an alternate indicator system. Theoxidase enzyme system contained in the reagent pad produces hydrogenperoxide which is used to convert the indicator with the assistance ofperoxidase which acts as the catalyst.

[0057] In the most preferred embodiment the reagents are impregnatedinto a porous membrane by submerging the dry membrane into a reagentdip. Excess fluid is wiped from the membrane surface and the membrane isgently dried in an oven. At this point, subsequent dipping and dryingcan be conducted. A preferred embodiment for a two dip process is:

[0058] MBTH-SO₄ & ALPS Formulation Final Concentrations A Dip In CitrateBuffer, pH 7  0.1 M stock A Dip EDTA 0.08% mannitol 0.19% Gantrez-S950.53% Klucel 99-EF 20 uM Crotein-SPA 7.45% enzyme reagents GlucoseOxidase 0.92% Peroxidase 0.54% B Dip In 70% Ethanol MBTH-SO₄ 0.66% ALPS2.00% SOS 0.20%

[0059] The assembly of a system kit comprised of a testing instrumentand a specific number of synchronized test strips for the testing of aspecific analyte can provide a simple, cost effective test method andprocedure.

[0060]FIG. 4 is a block diagram showing the processing operation of theinvention. Testing instrument 21 comprises a microprocessor 41 whichcontrols the operation of the testing instrument 21. The testinginstrument 21 is activated by a switching mechanism which may comprise amechanical ON button 34 and contacts 30-33 which close an appropriatecircuit when the button 34 is depressed. Closing of this circuittriggers operation of the device by notifying the microprocessor 41 thata measurement reading of a positioned test strip 11 is to be performed.The test strip may be one of a number of test strips in the set, and acounter keeps track of these. Alternatively, the circuit may be closedvia a fluid connection using the test sample, with the contacts 30 and31 operating as probes provided for making contact with the test pad 12of the test strip 11 to thereby activate the testing instrument 21 upondetection of the sample on the appropriately positioned test strip 11.

[0061]FIGS. 5A and 5B illustrate a method of confirming the wetting ofthe test pad 12 to start the testing instrument 21. The test strip 11 ofFIG. 5B is configured to have contacts 52 and 54 disposed on the testpad 12 thereof. The contacts 52 and 54 are spaced apart a finitedistance, and are only in electrical communication by virtue of a fluidcontact formed by the sample. The sample 16 is applied to the test strip11, wetting the test pad 12 and contacts 54 and 55. The contacts 54 and55 are in communication with contacts 30 and 31 on testing instrument 21so when wetted this completes a circuit which starts the testinginstrument 21 and begins the analysis of the sample. Of course, otheractivation schemes can be utilized by the invention. Two such schemesmay be optical or mechanical detection of the test strip 11 in dockingportion 37.

[0062] Following activation, measurement of the reaction of the samplewith the reagent on the test strip 11 is effected using the opticalsensor 45. Of course, the sensor itself need not be of the opticaltype—other expedients, such as electrochemical detection, e.g., fallwithin the purview of the invention. The microprocessor derives anelectrical signal from the sensor 45, comprising electro-optical devices50 and 52, and processes it to generate a detection signal indicative ofanalyte concentration in the tested sample. An ASIC 43(application-specific integrated circuit) and a memory, such as RAM(random access memory) 42 or a ROM (read only memory) may be used inconjunction with the microprocessor 41, while the results of themeasurement may then be displayed using LCD display 49. The results mayalternatively be stored in RAM 42 for subsequent viewing or processing.The subsequent processing may be performed using the measuringinstrument 21 itself, or using other devices to which the measurementresults can be downloaded. One possibility in accordance with theinvention is a modem link with a remote processing unit, using, e.g.,telephone lines. The information may also be downloaded for storage atan internet location or electronic bulletin board for subsequentretrieval and processing or review by medical professionals.

[0063] One feature in accordance with the invention is the use of acalibration chip 40 as shown in FIG. 4. The calibration chip isdetachably connectable to the testing instrument 21 for electroniccommunication with the microprocessor 41. It may be any form of volatileor non-volatile memory including single use microprocessors, EPROMs orEEPROMs thus forming an intelligent chip permitting intelligent datatransfer between the chip and the testing instrument 21. Calibrationchip 40 contains calibration information which is uniquely specific tothe reagent provided with a particular set of test strips 11 distributedwith the calibration chip. In this way, lot differences in the reagentcan be compensated for using the required information andsophistication, while at the same time obviating the need for the userto enter or contribute to this information. This minimizes error andgreatly facilitates use and accuracy of the testing instrument 21 of theinvention.

[0064] The color formed after applying the bodily fluid to the reagenttest pad is proportional to the amount of analyte in the applied sample16. The testing instrument 21, via sensor 45 and microprocessor 41,measures the change in reflectance due to the development of thespecific color generated by the reagent on the test strip 11. This iseither used as the input to a function which relates reflectance toanalyte level or to a table which correlates reflectance value toanalyte level. The function or the table must be stored within thesystem for it to produce and display, on display 49, a reading of theanalyte level in the sample 16. While most meters in use today employfunctions to convert reflectance readings to analyte concentration, thisapproach requires that the function be stable and well understood. Theuse of a look up table permits the storage of specific values forreflectance and their corresponding analyte levels. The testinginstrument uses this table and interpolates between the table values togive relatively accurate readings. This is achievable in a system suchas that described by this invention as the table can quickly begenerated for each reagent lot produced.

[0065] In the preferred embodiment, calibration is based on the responseproduced by a specific lot of test strips. In this manner, there is noneed to presort and test the LEDs 50 and 53, significantly reducing thecost of the sensor 45. In addition, this calibration step duringmanufacture allows the device to compensate for a wide area of variablesnormally found in reflectance systems. The specific calibration data forthe test strips 11 shipped with the testing instrument can be stored inthe unit's read only memory (not shown). Alternatively, a master stripcan be provided for setting the calibration information for that lot ofstrips and the master strip can be distributed therewith. A counter maybe provided to limit the testing instrument 21 to performing only aspecific number of tests which correlates to the quantity of test strips11 shipped with the device. Other limitations can be built-in, such asexpiration date information pertaining to the specific lot of teststrips 11, with this information being contained in the measuringinstrument's ROM or in the calibration chip 40 or in the master strip.

[0066] A more traditional approach to calibration may alternatively betaken. A calibration algorithm, with several settings if necessary,could be programmed into the system if the testing instrument has alonger projected life and is to be used with multiple sets of teststrips.

[0067] If a microprocessor is used for the calibration chip, the chipmay be provided with its own power source for memory informationretention. To prevent re-use when an EPROM or other memory device isused as the calibration chip, an optional mechanical latch 44 whichwould eliminate the ability to engage the calibration chip into thetesting instrument 21 a second time. Similarly, when a microprocessor orEEPROM or other memory device is used, the calibration chip 40 may haveits data overwritten or an indicator bit thereof be written by themicroprocessor 41 following its use to prevent reuse. The calibrationinformation stored in the calibration chip 40 is thus downloaded to theprocessor memory 42, and the calibration chip is disabled, preventingreuse thereof. The calibration information contains the permitted numberof test strip analyses to be performed, the number corresponding to thenumber of test strips provided with the kit. The calibration chip itselfcan then be disposed of.

[0068] Alternatively, a counter (not shown) may be provided in thecalibration chip, the counter being decremented each time the chip isread. In this manner, only a limited number of readings, correspondingto the number of test strips 11 provided with the calibration chip 40,can be performed. It is also contemplated that calibration informationprovides and expiration date preventing use of the calibration chipand/or associated strips thereafter, or a duration can be measured afterwhich use of the chip and/or associated strips is precluded. Theduration can be commenced from time of opening a package in which thekit is provided, or from any other similar time, such as the time offirst use of the calibration chip 40. The ordinarily skilled artisanwill find numerous variations can be effected without departure from thespirit and scope of the invention.

[0069] The patient uses the system by removing the testing instrumentfrom the packaging and placing it on a firm surface. The next step is toremove a test strip and insert it in the testing instrument. Insertingthe test strip activates the unit, eliminating the need for a poweron/off button or switch. The patient then uses either a sampler 60 (FIG.7) from the kit or one procured separately to draw a sample of capillaryblood. The kit may optionally be provided with a sampling device 62 aswell. The sample is applied to the test strip, initiating a timingsequence, and the testing instrument displays the results after anappropriate time. Alternatively, the patient may first apply the bloodsample to the test strip, then insert the strip into the testinginstrument to activate the test cycle and read out of test results.

[0070] The subject invention provides improvements over existingtechnology in use today in several ways. The preferred embodiment of theinvention eliminates the need for a patient to purchase a costly systemto conduct routine testing of body fluids. It also eliminates theexisting dependence on the customer to maintain the testing instrumentand monitor/compensate for reagent lot differences. The inventionprovides this easy to use format for analytes such as glucose byincorporating advanced lens based optics and low cost modem electronics.The use of lens based optics permits the system to focus on smallreaction area which reduces the size of the test pad. The resultingsmall test pad reduces the cost of the matrix employed and the quantityof expensive reagents needed to conduct an accurate assay using anoxidase and peroxidase chemistry. With a smaller test pad, a smallersample volume is adequate. The system conserves the energy used andminimizes the amount of light required by the system to determine thecolor change. The optics modules are calibrated during the manufactureof the testing instrument.

[0071] An important feature in accordance with the invention is themanufacture and calibration of the testing instrument 21 for use with aspecific quantity of test strips 11 which have been matched at thefactory. This limits the need for calibration codes, and minimizes themaintenance required by the patient in the form of cleaning, batteryreplacement and calibration code changes. It also improves the system'sability to provide long term accurate results because a testinginstrument is synchronized with only certain test strips. Once they havebeen used, a complete new kit is acquired with a testing instrumentcalibrated specifically for those test strips. This eliminates much ofthe compromise in system performance found in current products whichhave to work with strips made over a wide range of production conditionsand input states.

[0072] The above are exemplary modes of carrying out the invention andare not intended to be limiting. It will be apparent to those skilled inthe art that modifications thereto can be made without departure fromthe spirit and scope of the invention as set forth by the followingclaims.

What is claimed is:
 1. A synchronized detection device for detecting the presence of an analyte in a sample based on a physically detectable reaction of the sample with a reagent, the device comprising: a set of test strips each containing the reagent disposed thereon, each set containing at least one test strip; a calibration means corresponding to the set of test strips and containing calibration information uniquely characteristic to the reagent in the set of test strips; a housing having a docking portion for engaging at least one of the test strips; a sensor disposed at least partially in the housing and adapted to generate an electrical signal responsive to the reaction of the sample with the reagent; and a processor disposed at least partially in the housing and adapted to operate in accordance with the calibration means to generate a detection signal representative of the presence of the analyte in the sample.
 2. The device of claim 1, wherein the detection device is adapted for use a predetermined number of times corresponding to the number of test strips in the set, the predetermined number of times being tabulated by the processor, the processor disabling use of the detection device after the predetermined number of times.
 3. The device of claim 1, wherein the processor is adapted to disable use of the detection device after a predetermined date.
 4. The device of claim 1, wherein the calibration means comprises a chip containing correlation information for correlating the electrical signal to the detection signal.
 5. The device of claim 4, wherein the detection device is adapted for use with a plurality of said chips, each chip corresponding to an associated set of test strips and adapted to detachably connect to the housing.
 6. The device of claim 4, wherein the correlation information is based on a predetermined mathematical function.
 7. The device of claim 4, wherein the correlation information is based on a lookup table.
 8. The device of claim 5, wherein each chip is adapted for use a predetermined number of times corresponding to the number of test strips in an associated set, the predetermined number of times being tabulated by the processor, the processor disabling use of the chip after the predetermined number of times.
 9. The device of claim 5, wherein each chip is adapted for use up to a predetermined date, the processor disabling the use of the chip after the predetermined date.
 10. The device of claim 1, wherein the calibration means derives correlation information from a master test strip contained in the set.
 11. The device of claim 1, wherein the docking portion is adapted to positively locate the test strip in a predetermined orientation relative to the sensor.
 12. The device of claim 11, wherein the docking portion is adapted to matingly engage the test strip using engagement pins and corresponding holes such that only a successful mating achieves the predetermined orientation.
 13. The device of claim 1, wherein the sensor comprises at least one LED and associated photodetector.
 14. The device of claim 13, wherein the sensor comprises a first LED adapted to operate below a threshold radiation intensity and a second LED adapted to operate above the threshold radiation intensity.
 15. The device of claim 13, wherein the sensor comprises a first LED adapted to detect total reflectance from the reaction and a second LED adapted to measure reflectance of a predetermined color component of the reaction.
 16. The device of claim 13, wherein the sensor is provided with at least one molded lens optic system for focusing light.
 17. The device of claim 1, further comprising a memory for storing the detection signal.
 18. The device of claim 17, further comprising a modem for downloading the detection signal from the memory to a location remote from the detection device.
 19. The device of claim 18, wherein the modem is disposed in a communication module which detachably engages the detection device for communication therewith, and which communicates with a storage device located at the remote location.
 20. The device of claim 1, wherein the detection device is activated by an electromechanical switch triggered by the presence of a test strip in the docking portion.
 21. The device of claim 1, wherein the detection device is activated by an optical switch triggered by the presence of a test strip in the docking portion.
 22. The device of claim 1, wherein the detection device is activated by a pair of electrodes which sense the presence of the sample on a test strip disposed in the docking portion.
 23. The device of claim 1, wherein the sensor comprises a pair of electrodes in electrical communication with sample.
 24. The device of claim 13, wherein the photodetector is shielded from ambient radiation.
 25. The device of claim 1, wherein a set of samplers is provided with the detection device, the number of samplers corresponding to the number test strips.
 26. The device of claim 1, wherein the detection signal is displayed on a display disposed on the housing.
 27. The device of claim 26, wherein the display is an LCD device.
 28. The device of claim 4, further comprising a memory, the correlation information being uploaded from the chip and stored in the memory.
 29. The device of claim 28, wherein the chip is disabled following uploading.
 30. The device of claim 28, further comprising a mechanical latch preventing multiple uploadings.
 31. The device of claim 4, wherein the chip is provided with a counter, the correlation information being read by the processor a predetermined number of times corresponding to the number of test strips in an associated set of test strips, the counter being decremented with each reading.
 32. The device of claim 1, wherein the processor prevents use of the calibration means following a predetermined duration.
 33. The device of claim 1, wherein a sampling device is provided with the detection device.
 34. The device of claim 25, wherein a sampling device is provided with the detection device.
 35. The device of claim 4, wherein the chip is read once and disabled, the calibration information being stored for a specific number of tests corresponding to the number of test strips in an associated set of test strips.
 36. The device of claim 4, wherein the chip comprises an EEPORM.
 37. The device of claim 4, wherein the chip comprises a microprocessor adapted to permit intelligent data transfer. 